Compensated control



W. A. LEE ET AL COMPENSATED CONTROL Filed March 5, 1949 w ww sem n .w Tm w n m A f .w nH BAe I& h wn%T w July 15; 1952 Patented July 1571952 UNlTED STATES TENT OFFICE COMPENSATED CONTROL Walter A. Lee and John B. Brightman, Erie, Pa; assig'nors to General Electric Company, a corporation of New York 9 Claims. 1

This invention relates to controls for refrigerators and more particularly to controls which are modified by variations in the temperature of the air within the refrigerator.

In many refrigerators the food storage zone within the cabinet is cooled by an evaporator positioned within this zone and the temperature within the zone is controlled by a thermostatic bulb which is positioned on the evaporator and effects starting and stopping of the condensing apparatus depending on the temperature of the evaporator. With such a control arrangement the condensing apparatus is started and stopped at predetermined maximum-and minimum temperatures of the evaporator. With varying ambient conditions the particular evaporator temperatures chosen may not in all cases maintain the most desirable temperatures of the air within the refrigerated zone. This results from poor regulation in box air temperature, that is, the temperature of the air within the refrigerated food storage zone, as the ambient temperature changes. This regulation is improved, in accord- .ance with this invention, by effecting a lowering of the evaporator on and off limits as the ambient temperatureor usage load, or both, in-

crease.

In many refrigerators the evaporator includes a refrigerated shelf and the refrigerant from the condensing apparatus may pass first in heat exchange relationship with this shelf and then through the remainder of the evaporator. It has been common practice to position the control bulb in contact with an exterior surface of the evaporator. Under such conditions when the condensing apparatus is stopped in response to predetermined minimum temperature of the evaporator it has been found that applying a load to the refrigerated shelf causes an undesirable defrosting of this shelf before this load can affect the area of the evaporator Where the control bulb is positioned. By this inventionthe control bulb is mounted in heat exchange relationship with the shelf so as to be immediately affected by any load applied to the shelf thereby avoiding this undesirable defrosting. Furthermore, a structure has been provided for modifying the operation of the control in accordance with box air temperature.

Accordingly, it is an object of this invention to provide an improved refrigerator control including an element influenced by box air temperature.

It is another object of the invention to provide a refrigerator control responsive to evaporator temperature and including an improved arran ement for modifying this response in accordance with box air temperature.

It is a further object of this invention to pro vide an improved refrigerator control including a bulb positioned on the evaporator near the area of incoming refrigerant from the condensing apparatus and including an element engaging said bulb for modifying the operation of the control in response to box air temperature.

Further objects and advantages of my inven-- tion will become apparent as the following description proceeds. Features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification. r e

For a better understanding of this invention reference may be made to the accompanying drawing in which Fig. 1 is an elevation view of a portion of the refrigerator showing an evaporator and including a schematic representation of the remainder of the refrigerating system and the control switch; Fig. 2 is an enlarged sectional view taken on line 2--2 of Fig. 1; and Fig. 8 is a sectional elevation view of a portion of the control arrangement showing a modified form of this invention. 3 g

Referring now to .Fig. 1, there is shown a refrigerator i having an outer metal shell 2 and an inner metal liner 3. The space between the outer shell and the inner liner is closed by breaker strips 4 of suitable heat-insulating. material. The liner 3 defines a compartment or zone 5 to be refrigerated, and this zone is cooledby an evaporator 5 positioned in an upper corner of vthe compartment 5. The. evaporator is secured to the liner 3 by suitable fastening-devices, 'i.

The evaporator or cooling unit 5 includes an outer U-shaped portion 8 formed of. two pieces of sheet metal at least one of which is corrugated to provide passages for refrigerant. The portion I 8 of the evaporator may be of the general conrefrigerated by refrigerant circulated through tubing I2 which is secured in serpentine fashion to the underside of the plate which forms the shelf surface. v

The zone 5 to be refrigerated is cooled by the evaporator 6 through refrigerant circulated by the condensing apparatus shown schematically in Fig. 1. This condensing apparatus includes a motor-compressor unit, which is disposed within a hermetically sealed case l3, and a condenser l4. Refrigerant is circulated from the condenser l4 to the evaporator 6 through a restricting, or capillary, tube l5. The refrigerant passing from the condenser l4 enters the evaporator at the tubing l2 which is secured to the shelf 9. The other end of the tubing I2 is connected by a conduit IE to the main portion 8 of the evapo-.

rator, and the refrigerant in the closed refrigerating circuit passes from the tubing [2 through the conduit I6 to the portion 8 of the evaporator and circulates through this portion 8, the vaporized refrigerant passing into the header [1. From the header I! the vaporized refrigerant is conducted by a suction line Hi to the compressor within the case i3.

Refrigeration is controlled by the starting and stopping of the motor-compressor unit by a switch l9. Power is supplied to the motor from any suitable source through lines 20 and 2|, the engagement of the switch 19 with contacts 22 and 23 closing the circuit through the motor. In order to control the operation of the switch [9 a temperature-responsive control bulb 24 is positioned adjacent the evaporator. This bulb is connected by a tube 25 to a bellows represented schematically at 26. It can be seen that as the temperature of the bulb decreases the bellows 26 is caused to contract to open the circuit of the motor-compressor unit and as the temperature increases the bellows 26 is caused to expand to close the circuit of the motor-compressor unit. The use of a thermostatic bulb positioned adjacent the evaporator to operate a switch upon the occurrence of predetermined maximum and minimum temperatures of the evaporator, is, of course, old. However, it has been found that when an evaporator of the type shown is used and the thermostatic bulb is positioned on the portion 8 of the evaporator in the conventional manner, there is a tendency for the shelf 9 to defrost during the oiT-period of the condensing apparatus if a freezing load is applied to the shelf. This may result in an undesirable condition wherein ice and frost drops from the under surface of the shelf due to the increase of the temperature of the refrigerated shelf. This difficulty is overcome by positioning the control bulb 24 adjacent the shelf 9 so that any increase in the temperature of the shelf is immediately reflected in the control bulb. During the offperiod of the condensing apparatus relatively warm gaseous refrigerant from the condenser l 4 may pass into the tubing l2 of the refrigerated shelf but, by the arrangement shown, this relatively warm refrigerant affects the bulb 24 and changes its effective setting to start the operation of the compressor before undesirable defrosting of the shelf occurs.

It has been found further that a temperature control based on predetermined maximum and minimum temperatures of the evaporator may not be satisfactory in maintaining proper temperature conditions within the zone 5; for example, under high ambient temperature conditions a particular evaporator temperature setting may result in undesirably high temperatures in the box air within the zone 5 and under low ambient temperature conditions the same evaporator setting may result in undesirably low box air. Various arrangements have been employed to overcome this defect including the use of a plate or fin which is disposed in the path of the circulated box air to modify the response of the control. The arrangement set forth in the present application utilizes a fin or plate so disposed in the path of the circulating box air but a particular construction is employed which insures the modification of the operation of the control bulb in response to the box air temperature. Referring to Figs. 1 and 2 there is shown a metal plate or fin 21. This fin is mounted by screws 28 or other suitable fastening devices on a bracket 29. This bracket 29, which is L-shaped in cross section has one leg secured to the shelf 9. The control bulb 24 is mounted between an inclined leg 39 of the fin 21 and the bracket 29, the bulb being positioned in the corner formed by the two legs of the L- shaped bracket 29. In order to position the bulb 24 in heat exchange relationship with the evaporator and with the fin 21 a projection 3| is formed near the upper end of the vertical leg of the bracket 29. This projection 3| acts as a pivot point so that as the screws 28 are tightened the leg 30 of the fin 21 is pressed against the bulb 24 and presses the bulb into en agement with the bracket 29. Since the bracket is secured to the shelf 9 in any suitable manner, as by welding, the bulb is thereby also maintained in heat exchange relationship with the shelf 9 of the evaporator.

Because of the relatively large mass of the evaporator it might be possible for heat transmitted by the fin 21 to pass directly to the evaporator without sufiiciently affecting the bulb 24. In order to insure that the bulb is properly affected by the box air temperature through the fin 21, the can 21 and the bracket 29 are made of materials having thermal conductivity such that a preferential path through the bulb is provided. Thus, the fin 21 is made of a material, such as aluminum, having a high thermal conductivity, and the bracket 29 is made of a material, such as stainless steel, having a low thermal conductivity. Thus, by reference to Fig. 1 it can be seen that heat absorbed by the fin 21 and passing to the evaporator preferentially travels along a path extending through the fin 21 and the leg 30 thereof and thence through the control bulb to the evaporator, rather than through an alternate path from the projection 3| through the vertical leg of the bracket 29 to the evaporator. By the arrangement shown, therefore, the clamping of the bulb in heat exchange relationship with the evaporator and with the fin 21 is accomplished and, at the same time, a preferential path for heat flow is provided through the bulb so that the operation of the control is modified in response to the variation in box air temperature.

In Fig. 3 there is shown a modified form of this invention which further insures that the bulb is maintained in heat exchange relationship with the evaporator and the heat-conducting fin. In this form a bracket 29, corresponding to the bracket 29 in Fig. 1, includes a horizontal leg 32, which is secured to the refrigerated shelf 9 of the evaporator in any suitable manner, as by welding, an upwardly extending leg 33, and an inwardly inclined portion 34. A fin 21, which corresponds to the fin 21 in the form previously described, includes a leg 35 which is adapted to engage the control bulb 24, a second leg 36 which is generally parallel to the leg 33 of the bracket 29, and an inwardly inclined portion 31 which is adapted to engage the inwardly inclined portion 34 of the bracket 29. 1 The fin 21' is mounted on the bracket 25 by screws, one of which is indicated at 38. The screws 38 are arranged in threaded engagement with openings in the bracket 29'. It can be seen that as the screws 38 are tightened and the leg 36 of the fin 2? is thereby pulled toward the leg 33 of the bracket 29, the inclined surface 31 rides along the complementary inclined surface 34, and the fin 21 is forced slightly downwardly pressing the leg 35 against control bulb 24. The control bulb is thus firmly gripped between the leg 35 and the bracket 29 and is thereby maintained in heat exchange relationship with the fin 21' and the evaporator. As in the form previously described, the fin 21 is made of material of high thermal conductivity, such as aluminum, and the bracket 29' is made of a material of low thermal conductivity, such as stainless steel.

While specific embodiments of this invention have been shown and described, it is not desired that the invention be limited to the particular constructions shown and described and it is intended by the appended claims to cover all modifications within the spirit and scope of this invention.

What we claim is:

1. In a refrigerating apparatus, means defining a zone to be refrigerated, a cooling unit Within said zone, means for circulating'a cooling'fluid through said cooling unit, a bracket secured to said cooling unit, said bracket being composed of material of low thermal conductivity, a plate composed of a material of high thermal conductivity mounted on said bracket and extending into said zone so as to be affected by the temperature in said zone, a temperature-responsive control bulb positioned between said plate and said bracket, and means engaging said bracket and said plate at a point spaced from said cooling unit for maintaining said bulb in heat exchange relationship with said plate and. said cooling unit whereby said bulb is affected both by the temperature of said plate and the temperature of said cooling unit, said last-named means urging said bracket and said plate into engagement at a point spaced from said cooling unit.

2. In a refrigerating apparatus, means definin a zone to be refrigerated, a cooling unit within said zone, means for circulating a cooling fluid through said cooling unit, a stainless steel bracket secured to said cooling unit, an aluminum plate mounted on said bracket and extending into said zone so as to be affected by the temperature in said zone, a temperature-responsive control bulb positioned between said plate and said bracket, and means engaging said bracket and said plate at a point spaced from said cooling unit for maintaining said bulb in heat exchange relationship with said plate and said cooling unit whereby said bulb is affected both by the temperature of said plate and the temperature of said cooling unit, said last-named means urging said bracket and said plate into engagement at a point spaced from said cooling unit.

3. In a refrigerating apparatus, means defining a zone to be refrigerated, a cooling unit within said zone, means for circulating a cooling fluid composed of a material of high thermal conductivity mounted onsaid bracket and extending into said zone so as to be affected by the temperature in said zone, a temperature-responsive control bulb positioned between said plate and said bracket in heat exchange relationship with both said plate and said cooling unit, and means extending between said plate and said bracket at a point spaced from said cooling unit for pressing said plate against said bulb and for pressing said plate and said bracket into engagement at a point spaced from said cooling unit.

4. In a refrigerating apparatus, means defining a zone to be refrigerated, a cooling unit within said zone, means for circulating a cooling fluid through said cooling unit, a bracket secured to said cooling unit, said bracket being composed of material of low thermal conductivity, a plate composed of a material of high thermal conductivity mounted on said bracket and extending into said zone so as to be affected by the temperature in said zone, a control bulb positioned between said plate and said bracket in heat exchange relationship with both said plate and said cooling unit, and a screw engaging said plate and said bracket at a point spaced from said cooling unit for moving said plate into engagement with said bracket at a point spaced from said cooling unitto press said plate against said bulb.

5. In a refrigerating apparatus, means defining a zone to be refrigerated, a cooling unit within said zone, means for circulating a cooling fluid through said cooling unit, a bracket securedto said cooling unit, said bracket being composed of a material of low thermal conductivity, a plate composed of a material of high thermal conductivity mounted on said bracket and extending into said zone so as to be afiected by the temperature in said zone, and a temperatureresponsive control bulb positioned between said plate and said bracket, said plate including a leg adapted to engage said bulb, said plate and said bracket including spaced parallel portions, said plate and said bracket further including inclined portions in engagement with each other, and means engaging said bracket and said plate at said spaced portions to move said portions toward each other, said inclined surfaces riding on each other during such movement for imparting a component of motion to said plate in a direction effective to press said leg against said bulb.

6. In a refrigerating apparatus, means defining a zone to be refrigerated, a refrigerating system including an evaporator and a condensing apparatus for circulating refrigerant in a closed circuit, said evaporator being positioned within said zone and including a refrigerated shelf, the refrigerant from said condensing apparatus passing first in heat exchange relationship with said refrigerated shelf and then through remainder of said evaporator whereby warm gaseous refrigerant from said condensing apparatus passes first to said shelf during the off period of said condensing apparatus to affect the temperature of said shelf, and a temperature-responsive control bulb for governing the operation of said condensing apparatus mounted on said shelf and in heat exchange relationship therewith so as to be immediately affected by rise in the temperature of said shelf.

7. In a refrigerating apparatus, means defining a zone to be refrigerated, a refrigerating system including an evaporator and a condensing apparatus for circulating refrigerant in a closed circuit, said evaporator being positioned within said zone and including a refrigerated shelf, the refrigerant from said condensing apparatus passing first in heat exchange relationship with said refrigerated shelf and then through the remainder of said evaporator whereby warm gaseous refrigerant from said condensing apparatus passes first to said shelf during the off period of said condensing apparatus to affect the temperature of said shelf, a bracket composed of a material of low thermal conductivity secured to said shelf, a plate composed of a material of high thermal conductivity mounted on said bracket and extending into said zone, a temperature-responsive control bulb mounted on said shelf, and means engaging said bracket and said plate at a point spaced from said evaporator for maintaining said control bulb in heat exchange relationship with said shelf and said plate, said last-named means urging said bracket and said plate into engagement at a point spaced from said evaporator.

8. In a refrigerating apparatus, means defining a zone to be refrigerated, a refrigerating system including an evaporator and a condensing apparatus for circulating a refrigerant in a closed circuit, said evaporator being positioned within said zone and including a refrigerated shelf, the refrigerant from said condensing apparatus passing first in heat exchange relationship with said refrigerated shelf and then through the remainder of said evaporator whereby warm gaseous refrigerant from said condensing apparatus passes first to said shelf during the off period of said condensing apparatus to affect the temperature of said shelf, a stainless steel bracket secured to said shelf, an aluminum plate mounted on said bracket and extending into said zone, a temperature-responsive control bulb mounted on said shelf in heat exchange relationship therewith, and means engaging said bracket and said plate at a point spaced from said evaporator for maintaining said control bulb in heat exchange relationship with said shelf and said plate, said last-named means urging said bracket and said plate into engagement at a point spaced from said evaporator.

9. In a refrigerating apparatus, means defining a zone to be refrigerated, a refrigerating system including an evaporator and a condensing apparatus for circulating a refrigerant in a closed circuit, said evaporator being positioned within said zone and including a refrigerated shelf, the refrigerant from said condensing apparatus passing first in heat exchange relationship with said refrigerated shelf and then through the remainder of said evaporator whereby warm gaseous refrigerant from said condensing apparatus passes first to said shelf during the off period of said condensing apparatus to affect the temperature of said shelf, a stainless steel bracket of L-shaped cross section secured to said shelf, an aluminum plate mounted on said bracket and extending into said zone, a temperature-responsive control bulb positioned adjacent the corner of the L-shaped bracket in heat exchange relationship with said shelf, and means extending between said plate and said bracket for moving said plate toward said bracket to maintain said bulb in heat exchange relationship with said plate and said shelf.

WALTER AL LEE. JOHN B. BRIGITIMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,805,700 King May 19, 1931 1,878,301 Thomas Sept. 20, 1932 1,886,042 Osborne Nov. 1, 1932 1,960,802 Backstrom May 29, 1934 2,068,689 Miller Jan. 26, 1937 2,192,851 Tobey Mar. 5, 1940 2,333,899 Stickel 1 Nov. 9, 1943 

